In recent years, with diversification of information processing apparatuses, there has been a growing demand for flat panel displays having lower power consumption than cathode ray tubes (CRTs) and capable of being reduced in thickness. An organic EL panel is an example of flat panel displays that are advantageous in terms of low voltage drive, all-solid-state type, high-speed response, self light emission, etc. In an organic EL panel, thin film transistors (hereinafter referred to as the “TFTs”) are provided on, e.g., a glass substrate, a planarizing film is provided to planarize and insulate the substrate surface, and a first electrode, an organic layer, and a second electrode are sequentially stacked on the planarizing film.
The planarizing film is comprised of an organic resin material such as an acrylic resin or a polyimide resin, in view of the dielectric constant, the film thickness, easiness of planarization, easiness of patterning control, easiness of control of the taper angle at the end of a formed pattern. In particular, the acrylic resin is more advantageous than the polyimide resin in terms of the cost and in terms of the fact that the acrylic resin is a colorless, transparent resin while the polyimide resin is a colored, transparent resin. Thus, the acrylic resin is preferably used as the planarizing film.
These organic resin materials tend to accumulate water, oxygen, etc. therein as compared to materials comprised of an inorganic compound. In particular, the acrylic resin is more hygroscopic than the polyamide resin, and contains a larger amount of water than the polyamide resin. The water contained in the organic resin can be removed in advance by baking. However, for example, since the acrylic resin can resist heat up to about 250° C., the water contained in the acrylic resin cannot be sufficiently removed by the baking performed at a temperature lower than about 250° C. Thus, in the case where the planarizing film is comprised of the organic resin material, water etc. leaks from the planarizing film, and outgas from the planarizing film reaches the electrodes or the organic layer. Accordingly, the peripheral portions of the electrodes or the organic layer are damaged, and luminance is reduced in the degraded portions.
Patent Document 1 discloses a configuration in which inorganic insulating films are respectively provided in the layers located above and below a planarizing film comprised of an organic material. According to Patent Document 1, since the planarizing film is completely covered by the inorganic insulating films, the planarizing film can be prevented from absorbing water during manufacturing of an organic EL device, and degradation of the organic layer by the water can be prevented.
Patent Document 2 discloses an organic EL panel having a configuration in which a planarizing film is divided on a pixel-by-pixel basis by a planarizing-film dividing portion provided in a display region. According to this configuration, even if water leaks from the planarizing film in any of the pixels, the water is not allowed to move to the planarizing films in the other pixels, whereby the water leaking from the polarizing film can be prevented from diffusing in the entire display region.